When using a single-volume (“one-piece”) headrest, the adjustment travel along X is rather limited by the compatibility of the internal mechanism and the support structure, and by the style constraints imposed on headrests.
In order to increase the adjustment travel along X, the trend is toward a “dual-volume” solution where the front cushion of the headrest can be moved relative to a base structure in the central and rear area of the headrest.
Such a headrest is known from patent document FR2979867 originating from the Applicant. Another solution is disclosed in US Patent Application Publication No. 2010/0127541. In both cases, the position of the rear part of the headrest is unchanged and the thickness along the longitudinal direction (X) increases when bringing the front face closer to the user's head. However, the thicker the headrest in the longitudinal direction, the more the aesthetic appearance of the headrest is degraded and the more the visibility of the other occupants of the vehicle is affected, in some cases including the driver (field of vision partially obscured by the passenger headrest).
Another concern is related to safety in the event of an impact: this requires positive locking of the front face to prevent rearward travel, in order to protect the neck of the seat occupant in case of impact. In this context, known solutions such as those involving continuous deformation with an upper hinge region are not ideal.
There therefore remains a need to provide a headrest allowing wide adjustment in the longitudinal direction X, while limiting its volume (and therefore the obstruction of the view) and while maintaining compliance with load resistance specifications.